A series of Fe 2 O 3 -ZrO 2 mixed oxides (FexZr) were prepared by colloidal precipitation method using urea as mild hydrolyzing agent. The sulfate ions were grafted onto the surface of the mixed oxide by treatment with dilute sulfuric acid and subsequent thermal activation. The resulting sulfated grafted mixed oxides (SFexZr) were characterized using XRD, FTIR, Raman, surface area measurement, UV-Vis, XPS, TPD, FESEM and HRTEM techniques. XRD study indicated formation of a substitutional type solid solution in a limited composition range due to incorporation of iron ions into the zirconia lattice. The selective stabilization of the tetragonal phase of zirconia was observed in the mixed oxide system. The microstructural properties of the sulfate grafted mixed oxide were obtained from the Fourier analysis of the broadened XRD profiles. The presence of well dispersed iron oxide species in the zirconia lattice was ascertained from the Raman and UV-Vis study. XPS and FTIR study confirmed the presence of grafted sulfate functional groups. HRTEM analysis of the SFe10Zr sample revealed the presence of well dispersed mixed oxide particles with size in the range of 10-30 nm. The catalytic activity of the SFexZr material was evaluated for the synthesis of 1,8-dioxo-decahydroacridines by multicomponent condensation of dimedone, substituted aryl aldehyde and substituted anilines. A variety of dioxodecahydroacridines molecules were obtained with high yield and purity. The SFe10Zr material exhibited high surface area, enhanced sulfur retention and excellent catalytic activity for synthesis of the 1,8-dioxo-decahydroacridines molecules.
Zirconia nanoparticles were synthesized by precipitation, urea hydrolysis, amorphous citrate and combustion synthesis methods. The zirconia surface was subsequently modified by grafting Ba 2+ species. The Ba 2+ modified zirconia (Ba/ZrO 2) materials were characterized using XRD, Fourier analysis, UV-vis-DRS, FESEM and HRTEM techniques. XRD study indicated selective stabilization of the tetragonal phase of zirconia in the presence of Ba 2+ species. Fourier line profile analysis of the XRD peaks revealed that the average crystallite size of the zirconia nanoparticles is in the range of 5-15 nm. The surface area, basicity and barium content of the material depend strongly on the method of synthesis. The Ba/ZrO 2 catalyst prepared by urea hydrolysis method exhibited higher surface area and barium content compared to other samples. The catalytic activity of the Ba/ZrO 2 catalyst was evaluated for synthesis of β-nitro alcohols and 2-amino 2-chromenes. The β-nitro alcohols were synthesized by condensation of aryl aldehydes and nitromethane. Similarly, the 2-amino 2-chromenes were synthesized by condensation of arylaldehydes, α-naphthol and malononitrile. The Ba/ZrO 2 catalyst was found to be highly efficient for synthesis of both classes of compounds providing excellent yield and purity of the products.
In this study, a series of phosphate grafted SnO2–ZrO2 nanocomposite oxides are prepared via the urea hydrolysis method and evaluated as catalyst for synthesis of 3-substituted indoles.
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